The present invention relates to a clutch for vehicles, and more particularly to a clutch disk for a clutch used in an automobile, in which clutch disk a rust preventive is impregnated. There is a clutch disc having facings which are made of sintered steel. In such a clutch, moisture in the air tends to deposit on the sliding surfaces of the facings of the clutch disk, flywheel and pressure plate of the clutch moistening the surfaces, since these members are located closely to each other with an appropriate gap. Further the moisture inside the clutch of a vehicle hardly evaporates. Accordingly, rust easily forms on the inner parts. The rust formed on the sliding surfaces of the facings and the flywheel causes both members to stick to each other and causes problems with the clutch such as failure of disengagement of the clutch if the vehicle is not driven for a long time. Therefore, rust preventives must be provided on the sliding surfaces during manufacturing the automobile to prevent rusting which will occur before it is given to a user.
In a conventional rust prevention method, sodium nitrite is impregnated into the facings of the clutch disk and the surfaces made of iron of the flywheel and pressure plate are kept in a passive state, so that the formation of rust on the surfaces is prevented. In such a clutch disk, a sufficient amount of sodium nitrite must be maintained in the facings to obtain a satisfactory anti-corrosion effect.
However, the rust preventive of sodium nitrite is apt to be removed from the facing by the sliding of the facing on the flywheel during the use of the clutch for the transportation of the automobile before transfer of it to a user. As a result, sufficient rust preventing effect is not expected.